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Trout that might have been exposed to whirling disease – a parasitic organism that has severely impacted many trout fisheries in the nation – were stocked from a private hatchery in Colorado to several private waters here.
Arizona wildlife officials are asking anglers that may have fished for trout in those private waters to take preventive measures to help ensure the disease is not spread to other waters.
Testing by the Colorado Division of Wildlife determined that some of the fish from the Rainbow Springs Trout Ranch in southern Colorado were positive for whirling disease. The privately owned Trout Ranch has recently ceased operation.
Whirling disease can result in high mortality rates for young fish and has severely impacted fisheries in many other states and some other countries as well.
Arizona Game and Fish officials pointed out that the presence of the disease in Arizona fish has not been confirmed. "We have not confirmed that any infected fish have been brought into Arizona but we are in the process of determining that," advised Larry Riley, fisheries branch chief for the Arizona Game and Fish Department.
Arizona Game and Fish and the Arizona Department of Agriculture are working together along with other fish health professionals within the U.S. Fish and Wildlife Service, to develop and implement an aggressive plan of action.
Arizona Department of Agriculture state veterinarian, Dr. Rick Willer, said, "Whirling disease is not transmittable to people. And in fact, trout infected with the disease are safe to eat."
Whirling disease, or Myxobolus cerebralis, is a microscopic (metazoan) parasite that penetrates the head and spinal cartilage of fingerling trout where it multiplies very rapidly, putting pressure on the organ of equilibrium. This causes the fish to swim erratically (whirl), and have difficulty feeding and avoiding predators. The disease can result in high mortality rates for young fish.
Records from the Arizona Department of Agriculture and the Arizona Game and Fish Department indicate that 9,500 fish from the Rainbow Springs Trout Ranch were stocked at five different sites here.
"We cannot document that the fish came from lots or batches of trout that may have tested positive for whirling disease, but we must proceed under the assumption they have," Riley said.
Riley added that Game and Fish personnel have personally contacted all the private recipients of fish from the private Colorado hatchery and are working closely with them on possible remedies to eliminate risks to Arizona fishery resources from whirling disease.
The following sites have had trout provided to them from the Rainbow Springs Trout Ranch:
Lake of the Woods, Show Low;
White Mountain Country Club, Pinetop-Lakeside;
Forest Highlands, Flagstaff;
North Ranch, Flagstaff;
Perryman’s Pond, Happy Jack.
Game and Fish is requesting that anglers who have fished these waters clean their fishing gear with a solution of 10-percent chlorine bleach. "The likelihood of having fishing equipment or boots spread whirling disease is remote, but remote or not, the potential ramifications of spreading the disease in the state are too great. Therefore, we are asking that anglers help us out in protecting our valuable fisheries from the spread of this disease," Riley said.
It is important to note that this discovery does not involve state or federal trout hatcheries in Arizona nor does it appear to affect sensitive trout waters in Arizona - sites of naturally reproducing trout or sensitive native trout.
Arizona is one of the few Western states that has been free of whirling disease. Whirling disease is found in 22 states including: Alabama, California, Colorado, Connecticut, Idaho, Maryland, Massachusetts, Michigan, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oregon, Pennsylvania, Utah, Virginia, Washington, West Virginia and Wyoming and in several European countries, plus South Africa and New Zealand.
Among fish found in Arizona, rainbow, cutthroat and brook trout are the most susceptible species. Brown trout and grayling are considered less susceptible, and the disease has not been documented in Arizona’s two native trout, Apache and Gila, although biologists suspect they may be susceptible. Other species of game fish, such as bass or crappie, do not contract whirling disease.
In severe infections, the disease can cause high rates of mortality in young-of-the-year fish. Those that survive until the cartilage hardens to bone can live a normal life span, but are marred by skeletal deformities.
Whirling disease has a complex life cycle, which involves two hosts: trout and tiny aquatic worms called tubifex. Worms that become infected release a fragile state of the parasite that must infect a trout within a few days or perish.
Infected trout carry spores that are very persistent, but the trout can survive for years. The spores are released when an infected fish dies and decomposes. The whirling disease parasite can survive passing through the digestive tract of a predator and there is a remote possibility that the disease also can be transferred from place to place on muddy boots or equipment.
Uploaded: 9/1/2000
Uploaded: 9/1/2000